Whole System Acoustical Treatments  

Interior environments that are well designed strive to address all of the human sensory experiences within them. As such, the design process often pays ample attention to light quality and control as a visual sensory experience. Equally important, however, is the need to address sound quality and control as an auditory sensory experience, particularly in settings where audible speech is a primary activity such as educational buildings. This can have both immediate and long-term impacts on the users of these spaces. In the interest of achieving green or sustainable design, it is also incumbent on the designers to design, specify, and select systems and materials that not only provide effective acoustical performance, but also meet all of the relevant green building criteria.

Acoustics and Sustainability Overview

As the green building movement has developed in recent years, an increasingly recognized component that is helping to define a sustainable interior environment is acoustic performance. Just as daylight and views contribute to positive indoor environmental quality (IEQ) characteristics, so too, acoustic performance addresses the control of both wanted and unwanted sound in an indoor space. While acoustic performance has been a common part of many building design types, it has increasingly been the focus of attention in school buildings for a number of good reasons.

The U.S. Green Building Council (USGBC) has been a strong leader for the promotion of highly sustainable school environments through the LEED® for Schools Program. Within that specialized version of the LEED® rating system, acoustic performance is a specific criterion in two cases. First, there is a mandated prerequisite for minimum acoustic performance. The stated intent of this prerequisite is “To provide classrooms that are quiet so that teachers can speak to the class without straining their voices and students can effectively communicate with each other and the teacher.” While it would seem to many that this is a basic and commonly achieved criterion, the built condition in many school buildings indicates otherwise.

Some recently published work (February 2012) by Lindsay Baker at the University of California, Berkeley working with the Center for Green Schools at USGBC, and Harvey Bernstein, vice president, Industry Insights & Alliances at McGraw-Hill Construction, highlights some of the relevant issues. They have written a white paper titled “The Impact of School Buildings on Student Health and Performance: A Call for Research.” In it they point out that ample evidence exists that poorly designed classroom acoustics can actually have a negative impact on students' ability to hear and thus to learn. Among the things they cite:

Indoor environmental quality is enhanced in this interior space through design treatments that allow not only daylight, but also for proper acoustic control by addressing the wall and ceiling/floor assemblies and their surfaces.

 

“Research in classroom acoustics is a robust field in which a clear connection has been made between proper acoustic design in schools and acoustic performance. This performance in turn has a direct effect on speech intelligibility and therefore on student learning outcomes (Acoustical Society of America (ASA), 2009). One of the easiest ways to understand this connection is to imagine, as some researchers have simulated, what happens when students are unable to hear even 10% of a teacher's spoken words because of interferences in the acoustical environment. Many well-controlled studies corroborate the importance of low background noise level and speech intelligibility in maintaining appropriate acoustic conditions for student learning (Berg et al., 1996; Crandell & Smaldino, 1995; Knecht et al., 2002). Studies have also measured how unexpectedly poor many existing classrooms perform acoustically, demonstrating the extent of the problem (Feth & Whitelaw, 1999, Sato & Bradley, 2008).”

While this paper effectively states the issue of the prevalence of poor acoustical performance in schools, it is also being used as the basis to make the case for the need for more research in this area. Research such as this has been used to help develop ANSI Standard S12.60-2002, “Acoustical Performance Criteria, Design Requirements and Guidelines for Schools.” This national standard is used as a basis for determining currently acceptable levels of acoustic performance in schools and as a basis for demonstrating compliance with the LEED® acoustic performance requirements.

Beyond the LEED for Schools basic prerequisite requirement, there is also an additional IEQ credit for “Enhanced Acoustic Performance.” The stated intent of this credit is “To provide classrooms that facilitate better teacher-to-student and student-to-student communications through effective acoustical design.” In other words, it acknowledges the design efforts of improving acoustical design beyond the minimum prerequisite level to achieve better environments for speech communication and education. The basis for showing performance to earn this credit is also ANSI S12.60-2002. In order to achieve the this enhanced level of performance, a deeper understanding of acoustic principles and application strategies is required.

Interior Acoustics Fundamentals

There are four fundamental aspects used to address acoustical design that are the basis of most of the work and standards discussed above. Taken together, these form the essence of what is referred to as “whole system” acoustical design.

Background Noise

Noise in building spaces can come from a variety of sources such as building mechanical and electrical systems, outdoor activity such as transportation vehicles, or from people in adjacent indoor spaces. A certain amount of this noise in the background is certainly commonplace, but excessive background noise can seriously degrade the ability to communicate, thus making it more difficult for students to hear and for teachers to speak without raising their voices. It is generally accepted that most people would need to speak at least 15 decibels (dBA) louder than the background noise level in order to be heard at all. Therefore, ANSI Standard S12.60-2002 establishes some very stringent thresholds for background noise. Specifically, for core learning spaces of 20,000 cubic feet or less, the one-hour steady-state background noise levels should not exceed 35 dBA, while those over 20,000 cubic feet should not exceed 40 dBA. This is the same “faint” level of sound that one would experience in a quiet office. There is a caveat however that if the noisiest one-hour period during which learning activities take place is dominated by transportation noise, these maximum noise limits can each be increased by 5 dBA. The LEED prerequisite requirements follow these same ANSI thresholds for size and dBA levels of background noise, although it is only stated to address HVAC equipment noise.

Sound Transmission Class

With the acceptable background noise levels thus established, the building designers need to focus on achieving them by restricting unwanted sound from entering the spaces. This means creating wall, floor, and roof components or assemblies that first effectively block the amount of airborne sound transmitted through them. The measurement for this effectiveness is determined by a Sound Transmission Class (STC) rating. A higher STC rating means that more airborne sound is blocked by the component or assembly. Lower STC ratings mean that more sound passes through the components or assemblies adding to the background noise level in the space, degrading the ability to hear and understand speech.

It should be noted that, contrary to the popular notion that sound passes through a structure, such is not the case. Sound generated on one side of a wall will energize the wall structure and set it in motion, much like a diaphragm. The wall itself becomes the transmitter of the sound energy which can be heard on the opposite side of the wall by the listener. Hence, the ASTM test methods used to determine STC ratings have focused on this direct transmission process, although this testing has changed over the years meaning that STC results posted before 1999 may not produce the same results today. Currently, the STC number is derived from sound attenuation values tested at 16 standard frequencies from 125 Hz to 4000 Hz. These transmission-loss values are then plotted on a sound pressure level graph and the resulting curve is compared to a standard reference contour. Acoustical engineers fit these values to the appropriate Transmission Loss curve (TL) to determine a final STC rating. The measurement is accurate for speech sounds but less so for amplified music, mechanical equipment noise, transportation noise or any sound with substantial low-frequency energy below 125 Hz. As a supplement to STC ratings, Outdoor-Indoor Transmission Class (OITC) is a standard used for indicating the rate of transmission of sound between outdoor and indoor spaces in a structure that considers frequencies down to 80 Hz (Aircraft /Rail /Truck traffic) and is weighted more to lower frequencies. At least one significant research study considered students at a school in the regular flight path of an airport. After taking into account variables such as socioeconomic status, students in that school performed as much as 20% lower on a reading test than students in another nearby school (G. W. Evans & Maxwell, 1997).

In educational settings under ANSI Standard S12.60-2002, single or composite walls, floor/ceiling and roof/ceiling assemblies should provide specific sound transmission class (STC) ratings whenever separating a core learning space (e.g. a classroom) from other specific adjacent spaces as follows:

• STC-45 if the adjacent space is a corridor, staircase, office or conference room.
• STC-50 if the adjacent space is another core learning space, speech clinic, health care room or outdoors.
• STC-53 if the adjacent space is a restroom.
• STC-60 if the adjacent space is a music room, mechanical equipment room, cafeteria, gymnasium or indoor swimming pool.
• Classroom doors should be rated as STC-30 or more, and music room doors as STC-40 or more. Commonly, entry doors located across a corridor are staggered to minimize noise transmission from one room to another across the hallway.

It should be noted that open-plan classroom designs will not meet the requirements of this standard since there is nothing to impede the sound transmission from one space to another. In addition, STC ratings ranging from 45 to 60 are also outlined in the ANSI Standard for assemblies separating non-classroom spaces from adjacent spaces.

Ambient or Background Noise Level Is the totality of all sounds within the room when the room is unoccupied.

In an unoccupied space, sounds can be heard from a variety of sources. Careful scrutiny of the room can lead to identifying the intrusive sources. The diagram illustrates a few of the most common sources of noise. Illustration courtesy of Acoustical Surfaces, Inc.

The Sound Transmission Class is a rating of the effectiveness of a material or construction assembly to retard the transmission of airborne sound. The sound transmission loss between the source and receiving rooms are plotted on a graph by frequency and sound level in decibels. Once the appropriate contour has been selected the STC is determined by the decibel value of the vertical scale at 500 Hz. The STC is expressed as a single STC number (e.g. STC 32). Chart and photo courtesy of Acoustical Surfaces, Inc.

 

Impact Insulation Class

Beyond airborne sound, multi-story building designs need to address the resistance of structure borne sound, usually created by people walking or creating other impacts onto the floor/ceiling above the classroom space. Similar to STC ratings which address airborne sound, floor/ceiling assemblies can be tested or calculated based on Impact Insulation Class (IIC) ratings. These IIC ratings reveal the ability of a floor-ceiling assembly to absorb or deflect impact/structure borne noise and keep it from being transmitted to the space below. A floor/ceiling assembly with a low IIC rating will allow distracting noise to be transmitted into the room below leading to the associated problems of distraction and hampered communication. As such, Standard S12.60-2002 identifies specific ratings and recommendations for classroom learning spaces including the following:

• IIC ratings for floor-ceiling assemblies above core learning spaces should be at least IIC-45 and preferably IIC-50 as measured on floors without carpeting.
• In new construction, a gymnasium, dance studio, or other spaces with high floor impact activities shall not be located above core learning spaces.
• In existing facilities IIC-65-70 (depending on the volume of the space below) is recommended if gymnasia, dance studios or other spaces with high floor impact activities are located above core learning spaces.

Reverberation Time

Once the issue of background noise level is addressed by limiting the airborne and structure borne transmission of sound in a space, then a second significant item needs attention. Both LEED for Schools and ANSI Standard S12.60-2002 require that the Reverberation Time (RT) of sound within spaces is also controlled. Sound reflections are created when noise reverberates and echoes around architectural spaces. RT is the acoustical concept which measures how long, in seconds, it takes for these noises to become inaudible. This is quite a significant item since the selection of materials in the space are the direct cause of the reverberation and echoes, typically because their surfaces are hard and sound reflective rather than softer and absorptive. These echoes can impair what acoustical specialists call “speech intelligibility” since the echoes create garbled sounding words and impair verbal communication. Measuring Reverberation Time is important to determine the sound quality of speech and music in acoustical spaces. Instructional spaces, such as classrooms, are best with short RTs – less than 1 second to ensure clarity and high speech intelligibility. Speech generated in a space with a reverberation time of longer than 0.6 seconds is considered difficult to understand. Although some reverberation within a space can aid in speech distribution, longer reverberation times will cause a build-up of noise and thus degrade speech intelligibility. Auditoriums, theaters, and other musical spaces will typically benefit from longer RTs, typically greater than 1.5 seconds.

RT is determined by looking at both the volume and absorption rate in an acoustical space. The volume of a space is proportional to the RT of that space; the greater the volume, the longer the RT. Inversely, the amount of sound-absorbing material in any space will have a negative effect on the RT. As an example, a large space with tiled floors and a drywall ceiling will have a long RT. Conversely, a small room with a low suspended ceiling and high-pile carpet will have a much shorter RT.

Reverberation The time it takes for reflected sound to die down by 60 decibels from the cessation of the original sound signal (measured in seconds). - Reflected sound tends to “build up” to a level louder than direct sound. Reflected sounds MASK direct sound. - Late arriving reflections tend to SMEAR the direct sound signal.

In occupied space, the Reverberation Time affects the ability of people to understand spoken words (speech intelligibility) or hear other sounds clearly. Illustration courtesy of Acoustical Surfaces, Inc.

 

It is possible to calculate the reverberation time of sound within a space based on the interior surface qualities of a room. Using the process identified in ANSI S12.60-2002 to conduct these calculations, the resulting educational spaces must meet the following levels in order to comply:

• The maximum reverberation time for core learning spaces with internal volumes of greater than 10,000 cubic feet should not exceed 0.6 seconds.

• For core learning spaces with internal volumes of more than 10,000 but less than 20,000 cubic feet, the maximum reverberation time is 0.7 seconds.

• Reverberation time for spaces with more than 20,000 cubic feet of internal volume is not specified, however, guidelines are given in Annex C of the standard.

If an existing space or room is being investigated, then it can be tested with acoustical equipment specifically intended for measuring RT. For a new space, calculations must be relied on to determine what the RT will be in the proposed new or renovated space.

A recent study looked at classroom reverberation and children's performance and well-being in a set of classrooms in Denmark (Klatte et al, 2011). In classrooms with different RTs, they compared the children's short-term memory, speech perception abilities and attitudes about their classrooms and teachers. They compared classrooms with RTs from 0.49 to 1.1 seconds (the ANSI standard calls for a maximum of 0.6 as stated above) and found a significant negative impact on short-term memory and speech perception as reverberation time increased.

The amount of reflected sound compared to transmitted sound is directly related to the absorptive qualities of the acoustical material used in a room. Acoustic panels on this classroom wall help reduce echoes. Drawing and photo courtesy of Acoustical Surfaces, Inc.

Directly related to RT is the amount of sound energy absorbed upon striking a particular surface. The more sound energy that is absorbed then the less that is reflected back as an echo or reverberation. The commonly used scale to record different levels of such sound absorption is a Noise Reduction Coefficient (NRC) which ranges from zero to one: an NRC of 0 indicates perfect reflection while an NRC of 1 indicates perfect absorption. In actuality, it is the average of four sound absorption coefficients of the particular surface at specific frequencies of 250 Hz, 500 Hz, 1000 Hz, and 2000 Hz. These are the typical frequencies of human speech, and, therefore, the NRC provides a standardized, simple quantification of how well the particular surface will absorb the human voice. A more broad frequency range should be considered for applications such as music or controlling mechanical noise. Acoustical materials manufacturers often report NRC values higher than 1.0 due to the way the number is calculated in a laboratory. A test material's area does not include the sides of the panel (which are exposed to the test chamber) which vary due to its thickness. A certain percentage of the sound will be absorbed by the side of the panel due to diffraction effects.

A more detailed sound absorption rating is based on ASTM C423 and is known as the Sound Absorption Average (SAA). This is the average of the absorption coefficients for the 12 one-third octave bands from 200 to 2500 Hz. Hence, the SAA exceeds the range of testing of NRC which averages only four levels. Similar to the NRC, the higher the SAA, the better the material absorbs sound. Both the NRC and SAA values are single number ratings that indicate the level of sound absorption provided by the product being tested. However, the NRC value is rounded off the nearest 0.05 increment while the SAA value is rounded off the nearest 0.01 increment.

Selection Criteria for Acoustical Materials

Surface acoustical treatments such as bonded cotton provide a full range of performance characteristics along with a variety of colors and sound absorbing patterns to incorporate into designs. Photo courtesy of Bonded Logic, Inc.

The decisions related to selecting and specifying acoustical materials include a number of factors driven by good design principles and owner requirements. Clearly, the first item of consideration is the best acoustical performance in the space being designed or in the material assembly being constructed. STC ratings are typically based on the full assembly so determining all of the materials such as structure, framing, finishes, and penetration treatments is needed to obtain an accurate rating. Typically in order to achieve a desired STC rating within a space, particularly if the desired rating is on the higher end, then additional acoustical material is added. Commonly referred to as “sound insulation,” the choices of product are often similar to, and sometimes made from, the same material as thermal insulation since sound energy and heat energy are known to perform in a remarkably similar manner. Hence, just as adding insulation to a wall cavity reduces the amount of heat that flows through the wall, the same holds true for reducing the amount of sound that flows or is transmitted through that wall. And, just as there are choices in the types of thermal insulation that are used in buildings with correspondingly varying properties, so too there are choices in the type of sound insulation with varying properties. Insulation that is more tightly bonded, such as recycled cotton denim insulation, typically achieves higher STC ratings than comparable fiberglass insulation when incorporated into comparable wall assemblies based on independent testing.

Sound insulation can be manufactured from recycled materials such as newspapers for cellulose insulation or denim fabric for cotton batt insulation and surface treatments. Photos courtesy of Bonded Logic, Inc.

 

When it comes to improving reverberation times in a space, then the assembly is less important while the surface of exposed walls, ceilings, or floors takes over. In this case, the acoustical materials need to be selected based on their ability to absorb sound based on their NRC ratings. In any of these applications, all of their properties need to be considered including those listed below.

Fire Rating

For all building materials, fire rating is a significant concern. If acoustical materials are protected inside a wall or other building cavity, then the assembly may alleviate some of the fire rating need of the material. However, if it is located in a fire-rated assembly, then it needs to contribute to, not detract from, that fire rating. If, however, the acoustical material is placed on an exposed surface of the room being treated for RT, then the provisions of ASTM E-84 may well apply for fire rating and surface burning characteristics. Foam plastics are a particular concern in this case, while other materials that are not petroleum based can more easily meet these requirements.

Cost Effectiveness

The cost effectiveness of specified building materials is always a point of discussion, particularly when budgets are tight or subject to public scrutiny as in the case of public schools. Cavity insulation for controlling or improving STC ratings is generally considered a commodity and the cost may be very competitive across different manufacturers or material types, hence other factors may dominate the final selection decision. However, exposed treatments can vary widely in cost and appearance, so selecting the best solution for a particular application may require a bit more review. For example, interior panels could be fabricated from fiberglass insulation covered with fabric or from monolithic decorative acoustical cotton. While 2-inch fiberglass covered with fabric demonstrates similar acoustical performance to 2-inch acoustical cotton, the relative cost of the fabric covered fiberglass panel is more than 3 times as much. By performance contrast, 1-inch melamine covered foam acoustical panels cost more than 1-inch bonded cotton panels but only provide half as much acoustical absorption. Hence, it is important to compare not only the acoustic performance of a material, but also the thickness needed to achieve comparable performance between materials. Further, the surface treatment needs to be considered since it can add considerably to the cost. Obviously monolithic panels that don't require a separate covering will be more cost effective, and since they are often available in a variety of options including colors, design quality of the space can be maintained.

New products such as pre-measured perforated batts allow for faster and easier installation while minimizing waste on construction sites. Photo courtesy of Bonded Logic, Inc.

 

Green Construction

Sustainability and green principles are clearly important in all material selections, particularly if LEED® for Schools is being pursued. Clearly, maintaining the integrity of the green principles of the building means addressing all of the materials in the building, including the acoustical treatments. Therefore, beyond the acoustic qualities, the following should be considered:

New products such as pre-measured perforated batts allow for faster and easier installation while minimizing waste on construction sites. Photo courtesy of Bonded Logic, Inc.

 

• Selecting materials with recycled content. Sound insulation and surface treatments do not need to be manufactured from virgin materials. In fact some excellent products boast significant recycled content for the primary material as well as the added materials that form binders, treatments, etc. It is now possible and quite desirable to specify insulation that has significant percentages of both pre-consumer and post-consumer content, with post-consumer content preferred. Acoustic products that are manufactured from post-consumer content are now widely available throughout the United States. For example, both acoustic panels and batt insulation are currently available that are made from recycled cotton, or recycled denim in particular, that contain up to 80% recycled content by weight.
• Selecting rapidly renewable materials. Acoustic materials can be manufactured from a variety of raw materials, some of which are made from rapidly renewable sources such as cellulose or cotton fiber. Of course others are made from non-renewable sources like petroleum-based foam plastic. It is clearly preferable to specify such products which are now commonly available for up to 80% of their content by weight.
• Reducing construction waste. Materials that are easy to work with and can be readily installed into the building should produce less waste. Some acoustical batt insulation is available with perforations that allow for standard and irregular framing spaces to be efficiently filled with a reduction in waste. In all cases, specifying insulation that can be recycled instead of discarded if there is any surplus is clearly preferable and readily available.
• Selecting regional materials. This item is obviously dependent on the location of the building and the source of materials so it will not be possible for all projects. Nonetheless, where a source is within range of a building project, choosing acoustic materials that are locally available can contribute to regional material content in the building.
• Reducing embedded energy in materials. Many building product manufacturers that are serious about their own green processes will assess and identify how their product compares to others in terms of the energy used or the environmental impact of the manufacturing and delivery process. It is possible to select acoustic materials that demonstrate this quality which is sometimes inherent in the material choice itself. Petroleum-based products, for example, will contain inherently more embedded energy due to processing than natural, renewable products.
• Indoor air quality contributions. Some acoustic materials are better than others at avoiding indoor air quality problems. Since the material may be exposed to the interior space, selecting and specifying insulation that contains no harmful irritants or chemicals including no volatile organic compounds (VOC) is clearly important. Additionally, the ability of the acoustic materials, whether inside an assembly or exposed, to resist microbial growth is important in avoiding the presence of mold, mildew, or other health-related concerns in a space. Finally, selecting materials that pose no skin reactions either during installation or afterwards, contribute to the general health of those exposed to it. The good news for specifiers is that there are alternatives such as cotton fiber insulation and others that avoid many or all of these indoor air quality concerns.
• Innovation in green design. Using some of the acoustic principles discussed previously, it is quite possible to exceed the stated minimums for acoustic performance and be recognized for innovation credit.

Using a Whole System Approach to Acoustic Design

By now it is clear that there are multiple factors to consider in achieving the desired acoustical performance for green buildings and for school buildings in particular. As with all requirements in the ANSI Standard S12.60-2002, it is the architect or designer's responsibility to take the necessary steps in specification and design, but careful construction and installation will obviously be necessary to ensure compliance. To begin with, in order to meet the maximum background noise levels of 35 or 40 dBA called for, attention to sound needs to start early in the design phase of a project. Simple strategies such as locating noisy areas away from quieter areas help reduce the presence of sound in unwanted spaces to begin with. Then, the design of all of the wall, ceiling, and floor assemblies needs to be reviewed for meeting STC ratings and outdoor noise control. This will require some review of ratings of common construction assemblies, but also some calculations in order to verify and discern whether or not additional sound insulation or other measures are needed in these assemblies. In order to specifically address the HVAC system noise identified in LEED for Schools, close collaboration between project architects and engineers is crucial. The goal is to design and specify a complete HVAC system including equipment mounting, ductwork, etc. that can achieve a Noise Criteria of approximately 25-35 based on ASHRAE Fundamentals. This may require the use of duct liners or insulation that absorb and diminish the HVAC sound from equipment or airflow. Specific products are available for this and should be coordinated between the different design disciplines so they are properly specified and installed to perform quietly. It is also important to discuss sound control options with the plumbing and electrical engineers to isolate any background noise in those systems and address them in an appropriate manner.

Acoustic panels hung from ceilings improve the overall acoustic performance in those spaces. Photo courtesy of Acoustical Surfaces, Inc.

 

If a multi-story educational facility is being designed, then IIC ratings will be an important consideration in reducing background noise, particularly from upper floors. The floor/ceiling system should be specified and constructed in order to create spaces quiet enough to maintain the speech and teaching functions without distraction. Installing carpet on the floor above is one example of ways to reduce impact sounds. But it may also be necessary to isolate the finished floor from the structural floor or to isolate the ceiling from the floor above. For any vibrating machinery located on the floor above or on the roof structure, rubber pads or spring systems should be installed to avoid the creation of noise or its transfer.

Once the background, HVAC, and impact noise issues have been resolved, then the focus needs to turn to the control of reverberation within the interior spaces. Once again, it is the architect or designer's responsibility to ensure that a space meets the required reverberation times by providing the appropriate amount of sound absorption to control RT. Since the stated variables that affect the RT include the volume of the space and the amount of sound absorption within the room, both must be looked at. The volume is likely a function of the owner's program requirements, but the resulting size will have an impact on reverberation in general which the design professional needs to take into consideration. Then, in order to determine the amount of sound absorption present, a material's NRC multiplied by the surface area for the exposed materials in the space must be calculated. Once the amount of absorption for each material has been calculated, the sum of these will give the total amount of sound absorption within the room. Laboratory certified sound absorption coefficients should be available from all of the material manufacturers. In order to achieve the required reverberation time, acoustical treatments will likely be necessary on either the walls or the ceiling, or possibly both. When reverberation time is considered during the design phase, the acoustical treatments are then an integrated part of the design rather than an unwanted add-on.

Finally, the choice of material is critically important for many reasons as already discussed. But longevity and durability are also important for it to hold up over time and under normal use conditions. Some acoustic materials, for example, are generally considered to be impact- and abuse-resistant but when applied directly to a wall, their acoustical performance is very low. While their acoustical performance can be improved dramatically with the addition of fiberglass behind it, the increase in cost significantly surpasses the cost of other options that are also abuse resistant, non-abrasive, non-shedding on impact and weigh less. Similarly, hanging acoustical ceiling baffles are often considered for larger spaces to control RT and maintain sound qualities. Such baffles made from fiberglass can raise handling and indoor environmental quality issues due to their exposure to people. Renewable, natural materials, such as acoustic cotton, can be a cost-effective solution for durable, abuse-resistant acoustical baffles with high-performance noise-reducing characteristics without the handling or environment concerns.

Conclusion

Addressing all aspects of sound control and noise reduction beginning during the early design process of a building can yield some very positive results. These include the readily apparent acoustic qualities of the space with notably less background noise and fewer echoes due to shorter reverberation times of sound. But beyond these immediate auditory sensory benefits, the users of these spaces will be the true beneficiaries by reaping ongoing rewards. Teachers or others speaking in the rooms will find that they can communicate in normal voice tones and levels without extra exertion. Students and those listening will find that they can more easily understand what is being said, will have fewer distractions, and can expect to retain what they learn longer. All involved can take satisfaction in creating a whole system approach to sound control that creates a building that is well designed and meets this newest standard of sustainability.

 

	Bonded Logic, Inc. manufactures recycled insulating products that are good for both you and the environment in which you live. With a focus on performance and sustainability, Bonded Logic has a solution for your insulation challenges. www.bondedlogic.com
	Acoustical Surfaces, Inc. has been solving soundproofing, noise control, acoustical and vibration problems for over 25 years. ASI offers over 2,500 specialty soundproofing, noise control products and a full line of LEED eligible acoustical products. www.acousticalsurfaces.com